package com.pattern.proxy.Jdk;

import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;
import java.io.File;
import java.io.FileWriter;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/*
* 用来生成原代码的工具类
* */
public class GPProxy  {
    public static final String ln="\r\n";

    public static Object newProxyInstance(GPClassLoader classLoader,Class<?> [] interfaces,GPInvocationHandler h){
        try {
            //1.动态生产原代码.java文件
            String src=generateSrc(interfaces);
            //java文件输出磁盘
            String filePath = GPProxy.class.getResource("").getPath();
            File f = new File(filePath + "$Proxy0.java");
            FileWriter fw = new FileWriter(f);
            fw.write(src);
            fw.flush();
            fw.close();

            //3、把生成的.java 文件编译成.class 文件
            JavaCompiler compiler= ToolProvider.getSystemJavaCompiler();
            StandardJavaFileManager manager=compiler.getStandardFileManager(null,null,null);
            Iterable iterable = manager.getJavaFileObjects(f);

            JavaCompiler.CompilationTask task =
                    compiler.getTask(null,manager,null,null,null,iterable);
            Boolean call = task.call();
            if(call){
                System.out.println("成功");
            }else{
                System.out.println("失败");
            }
            manager.close();

            //编译生成的。class 文件加载到JVM中来
            Class proxyClass=classLoader.findClass("$Proxy0");
            Constructor c = proxyClass.getConstructor(GPInvocationHandler.class);
            f.delete();

            //5、返回字节码重组以后的新的代理对象
            return c.newInstance(h);
        }catch (Exception e){
            e.printStackTrace();
        }
        return null;
    }

    //生产原代码
    private static String generateSrc(Class<?>[] interfaces){
        StringBuffer sb=new StringBuffer();
        sb.append("package com.pattern.proxy.Jdk;"+ln);
        sb.append("import com.pattern.proxy.Person;" + ln);
        sb.append("import java.lang.reflect.*;" + ln);
        System.out.println(interfaces[0].getName());
        sb.append("public calss $Proxy0 implements "+interfaces[0].getName()+" {"+ln);
        sb.append("GPInvocationHandler h;" + ln);
        sb.append("public $Proxy0(GPInvocationHandler h) { " + ln);
        sb.append("this.h = h;");
        sb.append("}" + ln);
        for (Method m:interfaces[0].getMethods()) {
            Class<?>[] params=m.getParameterTypes();

            StringBuffer paramNames = new StringBuffer();
            StringBuffer paramValues = new StringBuffer();
            StringBuffer paramClasses = new StringBuffer();

            for(int i=0;i<params.length;i++){
                Class clazz = params[i];
                String type=clazz.getName();
                String paramName = toLowerFirstCase(clazz.getSimpleName());
                paramNames.append(type + " " + paramName);
                paramValues.append(paramName);
                paramClasses.append(clazz.getName() + ".class");
                if(i>0 && i< params.length-1){
                    paramNames.append(",");
                    paramClasses.append(",");
                    paramValues.append(",");
                }
            }
            sb.append("public "+m.getReturnType().getName() + " "+m.getName()+"("+paramNames.toString()+ ") {"+ln);
                sb.append("try{" + ln);
                    sb.append("Method m= "+interfaces[0].getName()+".class.getMethod(\""+m.getName()
                    +"\",new Class[]{"+paramClasses.toString()+"});"+ln);
                    sb.append(hasReturnValue(m.getReturnType())? "teturn ": ""+
                    getCaseCode("this.h.invoke(this,m,new Object[]{"+paramValues+"})",m.getReturnType())+";"+ln);
            sb.append("}catch(Error _ex) { }");
            sb.append("catch(Throwable e){" + ln);
            sb.append("throw new UndeclaredThrowableException(e);" + ln);
            sb.append("}");
            sb.append(getReturnEmptyCode(m.getReturnType()));
            sb.append("}");
        }
        sb.append("}" + ln);
        return sb.toString();
    }

    private static Map<Class,Class> mappings = new HashMap<Class, Class>();
    static {
        mappings.put(int.class,Integer.class);
    }

    private static String getReturnEmptyCode(Class<?> returnClass){
        if(mappings.containsKey(returnClass)){
            return "return 0;";
        }else if(returnClass == void.class){
            return "";
        }else {
            return "return null;";
        }
    }

    private static String getCaseCode(String code,Class<?> returnClass){
        if(mappings.containsKey(returnClass)){
            return "((" + mappings.get(returnClass).getName() + ")" + code + ")." + returnClass.getSimpleName() + "Value()";
        }
        return code;
    }

    private static String toLowerFirstCase(String src){
        char [] chars = src.toCharArray(); chars[0] += 32;
        return String.valueOf(chars);
    }

    private static boolean hasReturnValue(Class<?> clazz){
        return clazz != void.class;
    }
}
